Evaluation of freeze-thaw cycle effect on the performance of asphalt pavements mixed with and without fibers

Rubber modified binder is added to enhance the binding properties of the asphalt pavements as well as its thermal resistance in cold climate. Due to increasing costs of rubber modified binder in asphalt paving projects, researchers and highway agencies in Flagstaff, Arizona, USA have initiated a pilot study with adding fibers in the traditional rubber modified asphalt mixture and conventional asphalt mixtures. The first goal of this pilot study is to review the possibilities of producing fiber reinforced asphalt mixture, which has reduced cost and better performance under local environment, in comparison with the current rubber modified asphalt mixture. The second goal is to develop a systematic approach of investigating the effect of freeze-thaw cycles on the mechanical properties of different types of asphalt mixtures.;This pilot study comprises three phases. Phase one is designed to investigate the effectiveness of fiber by adding fiber reinforcement in the traditional rubber modified asphalt mixture. Phase two aims at evaluating the feasibility of using ASTM C666 apparatus in examination of the freeze-thaw cycle effect on the stiffness and relaxation characteristics of the asphalt mixture modified with fiber and rubber. Phase three compares the performance and economics of fiber reinforced conventional asphalt mixture with rubber modified asphalt mixture.;Two different overlay projects were constructed in the Flagstaff area and Northern Arizona University (NAU) campus in August of 2013 and May of 2014. Three different asphalt mixtures were used in these test sections; including the traditional Rubber Modified Asphalt (RMA), Fiber Reinforced Rubber Modified Asphalt (FRMA), and Fiber Reinforced Conventional Asphalt (FRA). Sample mixtures from the two overlay projects were collected during paving. Freeze-thaw cycles test and the bending beam rheometer (BBRs) test were conducted on the collected samples at the NAU construction material lab. The data collected from the tests were processed and analyzed to develop the mechanical properties of different mixtures. These mechanical properties, including creep stiffness, relaxation modulus and induced thermal stress, were then adopted to generate mechanical models for evaluating and predicting the low temperature thermal resistance of different types of mixtures. Field observation were also scheduled, in order to validate the lab prediction.